Preparation of printing surfaces for photographing



Mar 1955 G. L. MORRISON 2,704,410

PREPARATION OF PRINTING SURFACES FOR PHOTOGRAPHING Filed Aug. 8, 1952 @5 21W? filfiqqm I United States Patent PREPARATION OF PRINTING SURFACES FOR PHOTOGRAPHING George L. Morrison, Evanston, Ill.

Application August 8, 1952, Serial No. 303,391

6 Claims. (Cl. 41-24) The present invention relates to the art of printing and is particularly concerned with the preparation for photographing of printing forms containing raised or intaglio printing surfaces.

In the everyday production of certain types of gravure printing surfaces, for example, in the practice of the photogravure and rotogravure processes, the text and other material to be reproduced by the gravure printing surface are transferred to that surface by a process which requires the use of a photographically produced print or transparency of the material to be reproduced. In order to obtain such a print or transparency, it is the usual practice to set up a printing form containing type and/or type-slugs, and the various other printing surfaces which are to be reproduced. This form is then inked and an impression on paper is made therefrom. Finally, the inked imprint or impression is photographed, and the resulting print or transparency is used in the production of the gravure surface.

There are serious disadvantages to this procedure. Regardless of how well type, type-slugs, and printing plates are made, there is a substantial loss in the clarity of the outlines of the printing surface thereof during the inking and during the actual printing operation, and this loss is carried over in any photographic operation which involves photographing an inked impression made from such type or other printing surfaces. Also, the process requires careful make-ready of the form, the inking of the form, and the making of an impression on paper, all of which steps involve further time and require relatively skilled workmanship.

It is apparent that many of the difliculties inherent to the procedure described above and most of the disadvantages of that procedure could be avoided by the direct photographing of the printing form, and in the past, attempts have been made to do this. However, due at least part to the fact that a printing form is commonly made up of elements having very uneven reflecting powers, varying from the high reflectance of new, cast type, or type-slugs, to the low reflectance characteristic of, for example, an oxidized copper plate, very poor results have generally been obtained in direct photography procedures. In fact, the results have generally been so unsatisfactory that for many years, it was thought that the direct photography of printing forms was impractical, if not impossible.

One successful procedure which makes it possible to directly photograph printing surfaces contained in the usual printing form, which may include type of various kinds and varieties and printing plates made of various metals is disclosed in my prior application, Serial No. 20,214, filed April 10, 1948, now Patent No. 2,624,700. The present invention is an improvement of the procedure disclosed in the above-mentioned application in that the procedure as disclosed in the present application is simpler and can be carried out more rapidly than the procedure disclosed in my prior application.

The present invention, as above indicated, is concerned with the provision of a procedure whereby it is possible to directly photograph printing surfaces, and especially the printing surfaces contained in the usual printing form, which may include type of various kinds and varieties and printing plates made of various metals, so as to obtain a photographic negative or positive which can be used in the production of gravure and other printing surfaces by any of the known methods. The invention makes possible Patented Mar. 22, 1955 'ice the obtaining of a much better photographic print or transparency of type and other printing surfaces than has been possible by any of the heretofore known procedures. The procedure of the invention can be carried out in a minimum amount of time and with a minimum amount of effort and equipment. Moreover, the practice of the invention does not impair the type or plates contained in the printing form and does not interfere with the prior or subsequent use of the form or its components for conventional purposes.

The features of the invention and the procedures which I prefer to follow in practicing the invention will be made apparent in the accompanying drawings and in the following description of certain illustrative examples thereof.

in the drawings:

Figure l is a perspective view of a printing form containing various kinds of printing surfaces;

Figure 2 is a plan view of a portion of two different kinds of printing elements which comprise a part of the printing form illustrated in Figure 1; and

Figures 3 to 6, inclusive, are sectional views, taken along line 3-3 of Figure 2, illustrating various of the steps in the preparation of a printing form for photographing in accordance with the invention.

The printing form illustrated in Figure l is of conventional type, and as such, it includes the usual heavy metal chase 9 for containing the various components of the form, furniture (i. e., spacers) 11 and the usual locking Wedges or quoins 13 for holding the printing elements in place in the chase. As is well known in the art, the usual printing form may include newly cast type and/or type-slugs, slightly used type, old type that is dirty and oxidized, photo-engravings, stereotypes and electrotypes and other printing plates having surfaces which may be of copper, zinc, brass, steel, nickel, chrome, silver, etc. The type and/or type-slugs and the stereotypes are all made of type metal, and these elements alone or in combination usually comprise a major portion of the printing form. In the form illustrated in Figure l, a copper printing plate is illustrated at 15, a zinc plate at 17, an electrotype section at 18, a stereotype section at 19, and a type section which may be either single type and/or type-slugs at 21.

The manner in which the various printing surfaces contained in the printing form are prepared for photographing, in accordance with the invention, is illustrated particularly in Figures 2 through 6. In Figure 2, there is shown a plan view of two differing kinds of printing elements which might comprise a part of a printing form. One of these, the element 23, is made of type metal, and the other, the element 25, is a copper electro-plate which is backed with metal or a combination wood and metal back as indicated at 27.

The surface of the printing elements 23 and 25 are generally coated with oxides as indicated at 29 and 31 in Figure 3.

The first step in the preparation of the printing form is the removal of the oxide coatings which are generally present from the relief printing surface which is to be photographed. The oxides are preferably removed from the surfaces of all metals other than type metal in the printing form by chemical treatment. In order to minimize or prevent the reoxidation or spotting of the surfaces, as little water as possible should be present in the chemical solution used in the removal of these oxides. Common chemical solutions, well known to those skilled in the art, can be used to remove the oxides from the surface of the printing form. Volatile solutions are generally preferred since they shorten the time required for this operation. Examples of suitable solutions which may be used to remove the oxides from copper and zinc are: a 5 per cent solution of hydrochloric acid in anhydrous alcohol works very well on copper and to a lesser extent on zinc; a 10 per cent solution of sulphuric acid in anhydrous alcohol also works well on copper but is not as eflicient as the hydrochloric acid solution; and a 10 per cent solution of acetic acid in anhydrous alcohol produces very satisfactory results on zinc.

The appropriate chemical solution can be applied to a printing surface by placing a small amount of the chemical solution on a rubber block by spraying, dabbing, or the like and then passing this block over the printing surface. If the proper chemical solution is used, this treatment will be sufficient to remove the oxide coating from the metallic surface.

It is, of course, possible to remove the metallic oxides from the surface of metals other than type metal by other means than chemical treatment, for example, by abrading. However, since the removal of the oxides from such surfaces by abrasion generally takes a longer time, chemical treatment of the surfaces is preferred.

After the oxides have been removed from the metal surfaces other than type metal, the surfaces of all of the metals in the printing form are subjected to an abrasive treatment. This step serves the following functions: it removes the oxide from the surface of any type metal which might be present in the printing form; it removes any oxide which might be reforming on the surfaces of the metals other than type metal in the printing form; and it converts all of the metal surfaces into a substantial uniform matte finish which is a diifusively refleeting surface, fine enough to permit a high percentage of incident light to obey the cosine law. The resultant surfaces have sulficiently similar light reflectance characteristics to provide, after the hereinafter described process steps are carried out, a surface suitable for photographing.

The abrading can be accomplished in various ways,

but particularly satisfactory results are had when the abrading 1s accomplished by the use of a block of rubber or rubber-like compound containing very fine abrasive material. An ordinary pencil eraser is an example of such material, although a larger block such as is commonly used in the jewelry-polishing industries will be found more practical in commercial operations. The abrasive material contained in the block is preferably very fine, such as flour of emery, diatomaceous earth and the like. As previously stated, abrading removes dirt, oxides and the like and converts the printing surfaces in the form to clean, matte surfaces having uniform light diffusion properties; and for best results, the abrasive produced matte surface should not contain any lines large enough to be visible to the naked eye. A few light strokes of the abrasive-carrying block across the printing surfaces in the form are usually sufiicient to produce the desired result. Thus, both the abrading and the cleaning operations can be accomplished in a very short interval of time. The removal of the oxides from the printing surfaces is illustrated in Figure 4.

As the next step, the entire form is coated with a light-absorbing or non-actinic coating, preferably by spraying, although this coating can be applied in any other manner. This overall, non-reflecting coating is illustrated at 33 in Figure 5. Various materials can be used for the light-absorbing coating 33; the best cooatings, however, are those which include a suitable light-absorbing pigment dispersed in a suitable liquid vehicle. The sprayed coating should dry rapidly and should be readily removable from the printing surface, as is required in the next step of the preparation process; it should also be readily removable from all other parts of the printing form at the conclusion of the photographing operation. At the same time, the coating should not dust or crack, and it should not be toxic or difiicult to use.

A particularly satisfactory coating is produced by the mixture of two parts of trichloroethylene and one part lamp black, all parts being by volume. This coating dries immediately and is easily removed from the type and printing plate surface. Also, the material does not dust; it is cheap, easy to handle, and non-cracking.

It will be understood, however, that other types of coatings can be used. The essential thing is the provision of a coating which will not reflect actinic light. For example, it is possible to employ an alcohol-base coating, a suitable formula including one part shellac, six parts dry, drop-black, and eight parts methanol, all by volume. This coating dries very fast, but in order to make possible convenient removal of the coating from the printing surfaces which are to be photographed, it is necessary to ink the printing form before the coating is applied, as will be hereinafter described. It is also possible to use coatings which comprise dispersions of pigments other than drop-black, for example, red lead can be used quite successfully. Also, it is possible to spray the printing form with an optical black lacquer, but materials of this type are not recommended, due to the difiiculties experienced in cleaning the type and other components of the printing form.

As a final step in the preparation of printing surfaces in accordance with the invention, the non-reflecting coating which has been applied to the entire surface of the printing form is removed from the printing surfaces of the form. The non-reflecting coating which remains thus masks or covers the entire background of the printing form as illustrated at 33a in Figure 6, at the same time the metallic printing surfaces are completely exposed.

The removal of the non-reflecting coating from the printing surface is conveniently accomplished by the use of a flat rubber pad; a cloth-covered, rather firm, rubber block or equivalent means. If the coating has been applied by the use of the trichloroethylene-lamp black mixture described above, the rubber pad may be used dry and a few light strokes of the pad will effect adequate cleaning of the printing surfaces. If an alcohol type coating is used, the printing form should be inked preliminary to the application of the coating and the coating can be removed by using a rubber pad which has been moistened in naptha, benzene, or other ink solvent.

Upon the completion of the removal of the non-reflecting coating from the printing surfaces, the form is ready for photographing. This may be effected by the use of an ordinary photo-engraving camera, or otherwise. As pointed out in my copending application, Serial No. 63,037. which was filed on December 2, 1948, Patent No. 2,609,293, certain specialized illumination procedures are of particular advantage in photographing printing forms or other printing surfaces which may have been prepared as above described. After the form has been photographed, the background coating should be removed by brushing or by washing with a solvent.

The form may then be used for printing or making stereotypes or the like, or the form may be disassembled.

Various changes in the order of the various steps of the method may be made without departing from the scope of the invention. For example, the abrading step, or the chemical treatment step and the abrading step can be carried out after the non-actinic coating has been applied to the entire surface of the printing form and then removed from the relief printing surface which is to be photographed. However, when the steps are reversed in this manner, there is some danger that the nonactinic coating will be rubbed off of the background of the printing form.

In the foregoing, there has been described a new and improved method for preparing printing surfaces for photographing, and especially for preparing for photographing the various relief printing surfaces contained in the usual printing form. In the preferred method of practicing the invention, if the printing form contains printing surfaces of metals other than type metal, either with or without type metal, the oxide coatings of the surfaces of metals other than type metal are first removed by chemical treatment of the surfaces; next, the entire form is abraded so as to provide a uniform, clean, diffusively-reflecting surface on all of the relief printing surfaces in the form; the entire form is then sprayed with a non-reflecting coating; and finally, the non-reflecting coating is removed from the relief printing surfaces of the printing form. The resultant printing form can be photographed to provide a uniform density, sharp outline print or transparency of the printing surfaces contained in the form.

The practice of the invention does not in any way impair the printing surfaces on which it is used or prevent the subsequent use of such surfaces in ordinary printing operations. The procedure of the invention can be carried out rapidly and economically. At the same time, however, it provides a much higher quality print or transparency than has heretofore been available in the printing art.

This application is a continuation in part of my prior application, Serial No. 20,214, filed April 10, 1948, now Patent No. 2,624,700.

Various of the features of the invention believed to be new are set forth in the appended claims.

I claim:

1. The method of preparing for photographing a printing form containing relief printing surfaces of type metal,

and/or printing surfaces of at least one metal other than type metal, which comprises the steps of removing the oxides from each of the relief printing surfaces in the printing form, abrading the relief printing surfaces with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively-reflecting finish of suflicient fineness that the individual lines in the surface are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form and removing said coating from the relief surfaces while leaving the coatings intact on the other surfaces of the form.

2. The method of preparing for photographing a printing form which includes at least one printing surface of a metal other than type metal, which comprises the steps of chemically treating the relief printing surfaces of each of the metals other than type metal in the printing form to remove the surface oxides, abrading the relief printing surfaces of the entire form with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diifusively-reflecting finish of sufiicient fineness that the individual lines in the surface are not visible to the naked eye, applying a light-absorbing coating to the entire surface of the printing form and removing said coating from the relief surfaces while leaving the coating intact on the other surfaces of the form.

3. The method of photographing a printing form containing printing surfaces of type metal, and printing surfaces of at least one metal other than type metal, which comprises the steps of chemically treating the relief printing surfaces of each of the metals in the printing form other than type metal to remove the oxide coatings from said surfaces, applying a light-absorbing coating to the entire surface of the printing form, removing said coating from the relief surfaces while leaving the coating intact on the other surfaces of the form, and abrading the relief printing surfaces of the entire form with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively-refiecting finish of sufiicient fineness that the individual lines in the surface are not visible to the naked eye.

4. The method of preparing for photographing a printing form containing printing surfaces of type metal, and/ or printing surfaces of at least one metal other than type metal, which comprises the steps of applying a lightabsorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces While leaving the coating intact on the other surfaces of the form, removing the oxides from all of the relief printing surfaces in the printing form, and abrading the relief printing surfaces of the entire form with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively-refiecting finish of sufiicient fineness that the individual lines in the surface are not visible to the naked eye.

5. The method of preparing for photographing a printing form which includes at least one printing surface of a metal other than type metal, which comprises the steps of applying a light-absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the form, chemically treating the relief printing surfaces of each of the metals other than type metal in the printing form to remove the surface oxides, and abrading the relief printing surfaces of the entire form with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively-refiecting finish of sufiicient fineness so that the individual lines in the surface are not visible to the naked eye.

6. The method of preparing for photographing a printing form containing printing surfaces of type metal, and printing surfaces of at least one metal other than type metal, which comprises the steps of applying a lightabsorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the form, chemically treating the relief printing surfaces of each of the metals in the printing form other than type metal to remove the oxide coatings from said surfaces, and abrading the relief printing surfaces of the entire form with a clean resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively-reflecting finish of sufficient fineness that the individual lines in the surface are not visible to the naked eye.

References Cited in the file of this patent UNITED STATES PATENTS Alger Dec. 21, 1948 Morrison Jan. 6, 1953 OTHER REFERENCES 

